Twisted stem internal abrasive finishing tools such as are disclosed in Osborn Manufacturing catalog ABT-10 entitled, "Flexible Abrasive Brush Tools", and in co-pending patent Application Ser. No. 07/519,632 entitled "Abrasive Finishing Tool" are commonly used in the finishing of internal surfaces. These tools typically consist of individual plastic filaments containing abrasive material embedded homogeneously throughout which are placed in the bight of a cotter pin which is then clamped to form a slender shaft and twisted to hold the filaments in a radially extending arrangement. As shown in the Osborn catalog, the tool stems or shafts may be twisted to varying degrees to create a helical pattern of radially extending filaments. Such tools are effective in removing burrs, sharp edges, metal slivers from threaded bores, and in cleaning and finishing of curved internal surfaces.
The abrasive and cleaning action of such tools is accomplished primarily at the radial tips of the individual filaments which come in direct radial contact with the work piece surfaces. For applications in which the length of the filaments is approximately equal to the internal diameter of the hole to be abraded, only the tips of the filaments are utilized in the finishing process. It is desirable to have a greater portion than the tip of each abrasive filament come in contact with the work piece to increase the amount of abrasive material contacting with the work piece per revolution of the tool stem. This increases the working efficiency of the tool. However, in part because of the stiffness of the relatively short filament, it is difficult to insert an unmolded helical tool into an undersized hole. The axial curvature and bent back sweep induced into the filaments as they are forced into the hole is not of a controlled or permanent nature.
To apply a greater portion of each filament to the work piece, thereby putting a greater amount of abrasive material in contact with the work piece in a controlled and fixed manner, and increasing the working efficiency of the tool, it is desirable to have a finishing tool and a method to produce such tool in which the filaments are permanently positioned or set a transaxial in S-shape curve yet axially swept back configuration so that a portion of the length of each filament is put in contact with the work piece.